3D plotted PCL scaffolds for stem cell based bone tissue engineering

The ability to control the architecture and strength of a bone tissue engineering scaffold is critical to achieve a harmony between the scaffold and the host tissue. Rapid prototyping (RP) technique is applied to tissue engineering to satisfy this need and to create a scaffold directly from the scanned and digitized image of the defect site. Design and construction of complex structures with different shapes and sizes, at micro and macro scale, with fully interconnected pore structure and appropriate mechanical properties are possible by using RP techniques. In this study, RP was used for the production of poly(e-caprolactone) (PCL) scaffolds. Scaffolds with four different architectures were produced by using different configurations of the fibers (basic, basic-offset, crossed and crossed-offset) within the architecture of the scaffold. The structure of the prepared scaffolds were examined by scanning electron microscopy (SEM), porosity and its distribution were analyzed by micro-computed tomography (m-CT), stiffness and modulus values were determined by dynamic mechanical analysis (DMA). It was observed that the scaffolds had very ordered structures with mean porosities about 60%, and having storage modulus values about 1!107 Pa. These structures were then seeded with rat bone marrow origin mesenchymal stem cells (MSCs) in order to investigate the effect of scaffold structure on the cell behavior; the proliferation and differentiation of the cells on the scaffolds were studied. It was observed that cell proliferation was higher on offset scaffolds (262000 vs 235000 for basic, 287000 vs 222000 for crossed structure) and stainings for actin filaments of the cells reveal successful attachment and spreading at the surfaces of the fibers. Alkaline phosphatase (ALP) activity results were higher for the samples with lower cell proliferation, as expected. Highest MSC differentiation was observed for crossed scaffolds indicating the influence of scaffold structure on cellular activities

Effect of scaffold architecture and BMP-2/BMP-7 delivery on in vitro bone regeneration

The aim of this study was to develop 3-D tissue engineered constructs that mimic the in vivo conditions through a self-contained growth factor delivery system. A set of nanoparticles providing the release of BMP-2 initially followed by the release of BMP-7 were incorporated in poly(ε-caprolactone) scaffolds with different 3-D architectures produced by 3-D plotting and wet spinning. The release patterns were: each growth factor alone, simultaneous, and sequential. The orientation of the fibers did not have a significant effect on the kinetics of release of the model protein BSA; but affected proliferation of bone marrow mesenchymal stem cells. Cell proliferation on random scaffolds was significantly higher compared to the oriented ones. Delivery of BMP-2 alone suppressed MSC proliferation and increased the ALP activity to a higher level than that with BMP-7 delivery. Proliferation rate was suppressed the most by the sequential delivery of the two growth factors from the random scaffold on which the ALP activity was the highest. Results indicated the distinct effect of scaffold architecture and the mode of growth factor delivery on the proliferation and osteogenic differentiation of MSCs, enabling us to design multifunctional scaffolds capable of controlling bone healing.This project was conducted within the scope of the EU FP6 NoE Project Expertissues (NMP3-CT-2004-500283). We acknowledge the support to PY through the same project in the form of an integrated PhD grant. We also would like to acknowledge the support from Scientific and Technical Research Council of Turkey (TUBITAK) through project METUNANOBIOMAT (TBAG 105T508)

Incorporation of a sequential BMP-2/BMP-7 delivery system into chitosan-based scaffolds for bone tissue engineering

The aim of this study was to develop a 3-D construct carrying an inherent sequential growth factor delivery system. Poly(lactic acid-co-glycolic acid) (PLGA) nanocapsules loaded with bone morphogenetic protein BMP-2 and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocapsules loaded with BMP-7 made the early release of BMP-2 and longer term release of BMP-7 possible. 3-D fiber mesh scaffolds were prepared from chitosan and from chitosan–PEO by wet spinning. Chitosan of 4% concentration in 2% acetic acid (CHI4–HAc2) and chitosan (4%) and PEO (2%) in 5% acetic acid (CHI4– PEO2–HAc5) yielded scaffolds with smooth and rough fiber surfaces, respectively. These scaffolds were seeded with rat bone marrow mesenchymal stem cells (MSCs). When there were no nanoparticles the initial differentiation rate was higher on (CHI4–HAc2) scaffolds but by three weeks both the scaffolds had similar alkaline phosphatase (ALP) levels. The cell numbers were also comparable by the end of the third week. Incorporation of nanoparticles into the scaffolds was achieved by two different methods: incorporation within the scaffold fibers (NP–IN) and on the fibers (NP–ON). It was shown that incorporation on the CHI4–HAc2 fibers (NP–ON) prevented the burst release observed with the free nanoparticles, but this did not influence the total amount released in 25 days. However NP–IN for the same fibers revealed a much slower rate of release; ca. 70% released at the end of incubation period. The effect of single, simultaneous and sequential delivery of BMP-2 and BMP-7 from the CHI4–HAc2 scaffolds was studied in vitro using samples prepared with both incorporation methods. The effect of delivered agents was higher with the NP–ON samples. Delivery of BMP-2 alone suppressed cell proliferation while providing higher ALP activity compared to BMP-7. Simultaneous delivery was not particularly effective on cell numbers and ALP activity. The sequential delivery of BMP-2 and BMP-7, on the other hand, led to the highest ALP activity per cell (while suppressing proliferation) indicating the synergistic effect of using both growth factors holds promise for the production of tissue engineered bone.This project was conducted within the scope of the EU FP6 NoE Project Expertissues (NMP3-CT-2004-500283). We acknowledge the support to PY through the same project in the form of an integrated PhD grant. We also would like to acknowledge the support from Scientific and Technical Research Council of Turkey (TUBITAK) through project METUNANOBIOMAT (TBAG 105T508)

Single Tree Vegetation Depth Estimation Tool for Satellite Services Link Design

Attenuation caused by tree shadowing is an important factor for describing the propagation channel of satellite services. Thus, vegetation effects should be determined by experimental studies or empirical formulations. In this study, tree types in the Black Sea Region of Turkey are classified based on their geometrical shapes into four groups such as conic, ellipsoid, spherical and hemispherical. The variations of the vegetation depth according to different tree shapes are calculated with ray tracing method. It is showed that different geometrical shapes have different vegetation depths even if they have same foliage volume for different elevation angles. The proposed method is validated with the related literature in terms of average single tree attenuation. On the other hand, due to decrease system requirements (speed, memory usage etc.) of ray tracing method, an artificial neural network is proposed as an alternative. A graphical user interface is created for the above processes in MATLAB environment named vegetation depth estimation tool (VdET)

Biodegradable Hard Tissue Implants

Aging population and decreased physical activity due to increased life standards are two prevalent and inevitable factors that cause decrease in bone mineral mass, bone quantity, and muscle strength in the population. These consequences increase the incidence of bone fracture throughout the life of individuals. Although the bone has a great regenerative capacity compared to most other tissues or organs in the body, a proper healing of the bone requires appropriate alignment and fixation of fractured fragments throughout the process. There are different techniques and tools to provide bone substitutes with those properties. Most of the available fixation tools are made from non-eroding metals due to their inherent stiffness and toughness, the properties necessitated by the load bearing function of the skeletal system. Ideally, however, an implant should be temporary and be eliminated from the body as soon as its function is no longer necessary due to potential risks like late stage infection, bone resorption or immune reactions. For bone implants, due to the need for stabilization of fixation devices to the surrounding bone using screws or nails, removal operations may cause severe morbidity to the newly repaired fracture site. Another equally important problem with use of metal fixation devices is their superior mechanical properties that outweigh those of bone, lead the newly forming bone tissue not to be subjected to mechanical stimulation, which is a necessary requirement for bone forming machinery. Considering these problems, different biodegradable or bioerodible materials were suggested to be used in the production of temporary bone fracture fixation devices. This paper reviews the developments and trends in the field of biodegradable hard tissue implants, available materials, and their suitability to the host bone tissue.Старение населения и уменьшение физических нагрузок вследствие повышения уровня жизни являются превалирующими и неизбежными факторами, ведущими к уменьшению костной массы, минеральной составляющей костной ткани, а также снижению мышечной силы у современного человека. В результате этого увеличивается частота переломов на протяжении жизни. Хотя костная ткань обладает способностью к регенерации, сравнимой с другими тканями организма, существуют специфические особенности для восстановления ее целостности - сопоставление и фиксация отломков костей на время, необходимое для заживления. Разработаны различные технологии и средства, для придания заменителям костной ткани необходимых свойств. Большинство доступных средств фиксации изготавливают из некорродирующих металлов по причине их твердости и прочности, т.е. свойствам, обеспечивающим скелетной системе способность нести механическую нагрузку. В идеале, фиксирующий имплант должен быть временным, с возможностью удаления после восстановления нормальных функций, для предотвращения развития таких осложнений, как развитие имплантат-ассоциированных инфекций на поздних стадиях, резорбция кости или иммунные реакции. Операции по удалению фиксирующих имплантатов, вживленных в кость, нередко ведут к серьезным повреждениям новообразованной ткани костной мозоли. Другая, не менее важная проблема при фиксации металлическими средствами заключается в том, что металл обладает более высокими прочностными характеристиками по сравнению с костной тканью. Вследствие этого свойства металлических протезов механический стимул, являющийся необходимой физиологической составляющей для полноценности формирующейся кости, отсутствует. Исходя из необходимости решения данных проблем, предлагается использовать различные биодеградируемые и биоразлагаемые материалы для изготовления фиксирующих устройств при переломах кости. В статье дан обзор развития и трендов в области биодеградируемых имплантатов для твердых тканей, применяющихся материалов и их совместимости с костной тканью

Poly(ester-urethane) scaffolds: effect of structure on properties and osteogenic activity of stem cells

The present study aimed to investigate the effect of structure (design and porosity) on the matrix stiffness and osteogenic activity of stem cells cultured on poly(ester-urethane) (PEU) scaffolds. Different three-dimensional (3D) forms of scaffold were prepared from lysine-based PEU using traditional salt-leaching and advanced bioplotting techniques. The resulting scaffolds were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury porosimetry and mechanical testing. The scaffolds had various pore sizes with different designs, and all were thermally stable up to 300â °C. In vitrotests, carried out using rat bone marrow stem cells (BMSCs) for bone tissue engineering, demonstrated better viability and higher cell proliferation on bioplotted scaffolds compared to salt-leached ones, most probably due to their larger and interconnected pores and stiffer nature, as shown by higher compressive moduli, which were measured by compression testing. Similarly, SEM, von Kossa staining and EDX analyses indicated higher amounts of calcium deposition on bioplotted scaffolds during cell culture. It was concluded that the design with larger interconnected porosity and stiffness has an effect on the osteogenic activity of the stem cells.This work was supported by the European FP6 NoE EXPERTISSUES project (Grant No. NMP3-500283), the mini-project Fibrocell, TUBITAK (Grant No. TBAG 105 T508 Nanobiomat) and by METU-BAP

A high throughput approach for analysis of cell nuclear deformability at single cell level

Various physiological and pathological processes, such as cell differentiation, migration, attachment, and metastasis are highly dependent on nuclear elasticity. Nuclear morphology directly reflects the elasticity of the nucleus. We propose that quantification of changes in nuclear morphology on surfaces with defined topography will enable us to assess nuclear elasticity and deformability. Here, we used soft lithography techniques to produce 3 dimensional (3-D) cell culture substrates decorated with micron sized pillar structures of variable aspect ratios and dimensions to induce changes in cellular and nuclear morphology. We developed a high content image analysis algorithm to quantify changes in nuclear morphology at the single-cell level in response to physical cues from the 3-D culture substrate. We present that nuclear stiffness can be used as a physical parameter to evaluate cancer cells based on their lineage and in comparison to non-cancerous cells originating from the same tissue type. This methodology can be exploited for systematic study of mechanical characteristics of large cell populations complementing conventional tools such as atomic force microscopy and nanoindentation

Interaction of CO2 laser-modified nylon with osteoblast cells in relation to wettability

It has been amply demonstrated previously that CO2 lasers hold the ability to surface modify various polymers. In addition, it has been observed that these surface enhancements can augment the biomimetic nature of the laser irradiated materials. This research has employed a CO2 laser marker to produce trench and hatch topographical patterns with peak heights of around 1 μm on the surface of nylon 6,6. The patterns generated have been analysed using white light interferometery, optical microscopy and X-ray photoelectron spectroscopy was employed to determine the surface oxygen content. Contact angle measurements were used to characterize each sample in terms of wettability. Generally, it was seen that as a result of laser processing the contact angle, surface roughness and surface oxygen content increased whilst the apparent polar and total surface energies decreased. The increase in contact angle and reduction in surface energy components was found to be on account of a mixed intermediate state wetting regime owing to the change in roughness due to the induced topographical patterns. To determine the biomimetic nature of the modified and as-received control samples each one was seeded with 2×104 cells/ml normal human osteoblast cells and observed after periods of 24 hours and 4 days using optical microscopy and SEM to determine mean cell cover densities and variations in cell morphology. In addition a haeymocytometer was used to show that the cell count for the laser patterned samples had increased by up to a factor of 1.5 compared to the as-received control sample after 4 days of incubation. Significantly, it was determined that all laser-induced patterns gave rise to better cell response in comparison to the as-received control sample studied due to increased preferential cell growth on those surfaces with increased surface roughness

Interior Hygiene: Body, Space, Society, Ideals in the Modernist Turkish Context

The focus of this paper is the significance of the modern bathroom in Turkey, its meaning in the modernization of interiors, in terms of hygiene as a precaution for crises, as well as sanitary ware, and Turkish company VitrA’s role in continuously emphasizing the modern bathroom and challenging behavioral habits through design competitions, from the 1940s onwards.Among one of the most important spaces of hygiene, the bathroom was instrumental in bringing Western habits into the modern Turkish house. Hygiene was a matter of modern national identity emphasized in the Ottoman Empire at the turn of the century, even before the foundation of the Turkish Republic in 1923.The Western ideals of comfort and hygiene, bodily practices, and lavatory fixtures all contributed to the understanding of the modernization process of Turkish interiors. Moreover, a bathroom that combined the Western and today’s internationally accepted alla franga lavatory, a sink and a bath, thus combining these activities became a household application and a reflection of modern life. In the 1950s and 1960s, as the average urban Turkish family life moved to apartments that often housed governmental civil servants, the modern bathroom became a standard household space. Meanwhile, the alla turca lavatory, a lavatory on which one has to crouch, and that is still used in certain parts of Turkey and Asia, represented the uncivilized and unhygienic.With the modernization of the domestic interior, a transformation of wet allocation spaces took place, leading to the questioning of the domestic and public. Moreover, new materials and bathroom equipment were introduced, and bathroom equipment competitions were established, leading to inventions that synthesized habits of the East and the West, reaching a new hygienic standard regarding relevant potential crises. Both the company history of VitrA Eczacıbaşı and the competing designs are showcased in the paper, aiming to support an understanding of social and spatial change in the modern Turkish domestic interior that has redefined identity with proactive lessons for the future

Nano/microparticle incorporated chitosan fibers as tissue engineering scaffolds

[Excerpt] The aim of this study was to develop a bone tissue engineering scaffold with an inherent bone morphogenetic proteins BMP-2 and BMP-7 sequential delivery system. BMPs were encapsulated in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(lactic acid-co-glycolic acid) (PLGA) nano/microparticules which are then introduced to a chitosan matrix by two methods: embedding in the chitosan fibers and then forming the scaffold or by forming the chitosan scaffold and then introducing the nano/microparticules. [...]info:eu-repo/semantics/publishedVersio